Heating and air conditioning ducts normally extend from a plenum to an opening in a wall or floor. The outlet units installed in these openings usually have some sort of mounting flange attachable to the surrounding panel structure, and some arrangement for connecting the outlet unit to the remainder of the duct system. The present invention is associated with a type of installation frequently encountered in recreational vehicles, in which the outlet duct is installed in an opening in a wall panel, and connected to the plenum by flexible ducting consisting essentially of fabric surrounding an open-wound helical wire, which maintains the shape of the duct and permits relatively sharp turns. The outlet units are normally provided with some form of grille, which may provide louvre surfaces inclined to the axis of the air flow. Rotatability of the grille with respect to the outlet gives some degree of directional control over the air flow. The extensive use of these devices justifies the application of high-production molding techniques, and competitive factors cause very small differences in the cost of manufacture to become very significant.
The following patents have been noted as of general interest in connection with these outlet devices:
______________________________________ Germonprez 1,952,707 1934 Mattingly 2,733,889 1956 Fadow 3,333,522 1967 Eggers 3,570,387 1971 ______________________________________